/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.nutch.indexer;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.nutch.plugin.Extension;
import org.apache.nutch.plugin.ExtensionPoint;
import org.apache.nutch.plugin.PluginRepository;
import org.apache.nutch.plugin.PluginRuntimeException;
import org.apache.nutch.storage.WebPage;
import org.apache.nutch.util.ObjectCache;

/** Creates and caches {@link IndexingFilter} implementing plugins. */
public class IndexingFilters {

	public static final String INDEXINGFILTER_ORDER = "indexingfilter.order";

	public final static Logger LOG = LoggerFactory
			.getLogger(IndexingFilters.class);

	private IndexingFilter[] indexingFilters;

	public IndexingFilters(Configuration conf) {
		/* Get indexingfilter.order property */
		String order = conf.get(INDEXINGFILTER_ORDER);
		ObjectCache objectCache = ObjectCache.get(conf);
		this.indexingFilters = (IndexingFilter[]) objectCache
				.getObject(IndexingFilter.class.getName());
		if (this.indexingFilters == null) {
			/*
			 * If ordered filters are required, prepare array of filters based
			 * on property
			 */
			String[] orderedFilters = null;
			if (order != null && !order.trim().equals("")) {
				orderedFilters = order.split("\\s+");
			}
			try {
				ExtensionPoint point = PluginRepository.get(conf)
						.getExtensionPoint(IndexingFilter.X_POINT_ID);
				if (point == null)
					throw new RuntimeException(
							IndexingFilter.X_POINT_ID + " not found.");
				Extension[] extensions = point.getExtensions();
				HashMap<String, IndexingFilter> filterMap = new HashMap<String, IndexingFilter>();
				for (int i = 0; i < extensions.length; i++) {
					Extension extension = extensions[i];
					IndexingFilter filter = (IndexingFilter) extension
							.getExtensionInstance();
					LOG.info("Adding " + filter.getClass().getName());
					if (!filterMap.containsKey(filter.getClass().getName())) {
						filterMap.put(filter.getClass().getName(), filter);
					}
				}
				/*
				 * If no ordered filters required, just get the filters in an
				 * indeterminate order
				 */
				if (orderedFilters == null) {
					objectCache.setObject(IndexingFilter.class.getName(),
							filterMap.values().toArray(new IndexingFilter[0]));
					/* Otherwise run the filters in the required order */
				} else {
					ArrayList<IndexingFilter> filters = new ArrayList<IndexingFilter>();
					for (int i = 0; i < orderedFilters.length; i++) {
						IndexingFilter filter = filterMap
								.get(orderedFilters[i]);
						if (filter != null) {
							filters.add(filter);
						}
					}
					objectCache.setObject(IndexingFilter.class.getName(),
							filters.toArray(
									new IndexingFilter[filters.size()]));
				}
			} catch (PluginRuntimeException e) {
				throw new RuntimeException(e);
			}
			this.indexingFilters = (IndexingFilter[]) objectCache
					.getObject(IndexingFilter.class.getName());
		}
	}

	/** Run all defined filters. */
	public NutchDocument filter(NutchDocument doc, String url, WebPage page)
			throws IndexingException {
		for (IndexingFilter indexingFilter : indexingFilters) {
			doc = indexingFilter.filter(doc, url, page);
			// break the loop if an indexing filter discards the doc
			if (doc == null)
				return null;
		}

		return doc;
	}

	/**
	 * Gets all the fields for a given {@link WebPage} Many datastores need to
	 * setup the mapreduce job by specifying the fields needed. All extensions
	 * that work on WebPage are able to specify what fields they need.
	 */
	public Collection<WebPage.Field> getFields() {
		Collection<WebPage.Field> columns = new HashSet<WebPage.Field>();
		for (IndexingFilter indexingFilter : indexingFilters) {
			Collection<WebPage.Field> fields = indexingFilter.getFields();
			if (fields != null) {
				columns.addAll(fields);
			}
		}
		return columns;
	}

}
